Geostationary communication satellites have to be positioned in precisely defined space segments assigned by the International Telecommunication Union (ITU) to each satellite. Due to drift the position of a satellite may change and has to be corrected so that it becomes necessary to determine precisely the position and/or movement of the satellite usually addressed as ranging. When analogue signals are send to and received from the satellite several ranging systems have to be used based on precise measurements of the time of travel of the analogue signals. For example, the vertical and/or horizontal synchronization pulses of television signals were used for measuring the travel time of the analogue TV signal. Such signal markers are not available when digital signals are transmitted.
Ranging of satellites, as it should be understood for the purpose of understanding invention to be discussed further below, stands for the task of determining the distance between a ground station and a satellite, especially a geostationary satellite. As an additional aspect, the ranging of satellites may be understood to also but not necessarily comprise the determination of the satellite velocity as the availability of a velocity value provides additional options while determining the distance between the satellite and a ground station and/or controlling the position of the satellite.